Process of producing mechanical negatives.



; STATES PATENT OFFICE.

OZIAS DODGE, 0F NORWICH, CONNECTICUT.

PROCESS OF PRODUCING MECHANICAL NEGATIVES.

No Drawing.

' ed impression, for example, without the use of a photographic plate; and the objects of my invention are: 1st. To transform a drawing, with all its radations of shading, into a photographica ly opaque stencil or negative, which gives all the delicacy and detail of the original. 2nd. To provide to photo engravers, artists and lithographcrs new means forproducing printing surfaces upon copper, zinc, lithographic stone, and the like,

and to produce printing surfaces electrolyti- 1 cally built up, without the use of a camera. 3rd. To preserve I a faithful negative of original drawings or printed impressions for indefinite further uses.

invention consists in transforming a drawing or printed impression made upon a transparent surface, such as the film patented to me December 24, 1907, so that it shall become a photographically opaque ne ative.

rior to my invention there was no method of obtaining a negative except by using a photographic plate, whereas by my present invention the surface bearing the drawing or printed image becomes the negative, and inthe place of the drawing there are transparent lines upon an opaque ground; and here my invention ends, but the uses of this negative in producing printing surfaces for the photo engraver, for artists, and for lithographers, and in producing relief plates built up electrolytically, will at once be seen and appreciated by those skilled in the art.

ll will now describe my improved process in its best form as now practised by me. The starting materials are, pre er'ably, a grained gelatin film, of a coarse, velvet or medium rain best suited to the nature of the drawing, and a pencil or ink especially prepared, which is soluble in gasolene or similar liquids, and insoluble in alcohol or Specification of Letters Patent.

Patented Dec. 15, 1914.

Application filed April 18, 1912. Serial No. 691,741.

water. On the grain side of this film the drawing is executed with such pencil or ink, and should show a grain in all parts except the deep black, and high lights should be taken out with a scraper.. I prefer not to use a rubber, but to erase with a cloth mois tened with gasolene if extensive erasures are needed, or to clean oif the entire drawing. The completed drawing is like any other drawing, only resting on a transparent support, and can be best judged by laying it face down upon white and looking at it from the back.

In the case of printed impressions, roofs are printed as guides in adding work or the production of several plates for color printing, thereby insuring a register as they are identical except for the individual work on or around the proof. These proofs are printed upon the film above mentioned in an ink soluble in gasolene or similar liquids if the printed image is to become the transparency with the additions and work upon them, or in an ink not soluble in the above liquids if they are only to serve as guides in'laying in the original work 'to make the various plates for color printing. As the proofs and work upon them are on a trans-- parent film they can be laid one over the other to advantage to judge how the final picture will be built up from the'various plates. This drawing or printed impression is now to be converted into a reverse printing negative for the sensitized zinc or copper plate, b covering the face of the drawing and the (i In supporting it with a photographically opaque varnish, composed preferably of a sdlution of shellac and alcohol, to which I add red and yellow dyes, making it opaque to actinic rays oflight. This varnish is so balanced hygroscopically that it unites to a slight depth with the film, rendering it opaque to actinic light and covers the drawing as well as the face of the film supporting it. The drawing should be dusted oif before applying the varnish, andno varnish should be allowed to run onto the under side of the film. In small work, the varnish may be applied by flowing; or if the drawing is large, or difficulty 1s experienced in flowing it, the drawing may "be varnished with a thick camel hair or water-color brush well loaded with varnish, by beginning at the top and carrying as wide a band of color as the brush will allow straight across, the second stroke just overlapping the lower edge of the first, and continuing thus to the bottom. I then dry the varnish, warming the film slightly while drying, and this stage may occupy from three to five minutes.

When dry I lay the film fiat upon clean paper and rub the surface lightly with a cloth or cotton moistened with gasolene or similar liquids, by which the drawing or printed proof is removed, leaving a red film stencil or photographic printing negative; and with the production of this negative, my present process is complete.

I will now describe the specially prepared ink which .I prefer to use, and the special pencil which I prefer to use in maklng the drawing above referred to. The ink is com posed of tallow, wax, soap and shellac in about equal parts, to which is added a fine Paris block for, color. This ink is cast into sticks and in use is rubbed up with water as with lithographic writing ink. The pencils are composed of similar materials with a larger proportion of wax, or ordinary lithogra hic pencils can be used.

c formula and directions for making the varnish are as follows: 32 ounces grain alcohol, 2 ounces dry shellac, common brown shellac sufiices. These I shake well together and allow them to stand from three to four days. The clear liquid is then decanted off from the precipitate. To 32 ounces of the liquid are added one ounce of water, 300 grains of auramin, soluble in alcohol, yellow dye, and 280 grains of rhodamin, soluble in alcohol, red dye. When the color is finally dissolved, the solution is filtered and is then ready for use as above described; giving if applied under the foregoing directions, a perfectly even color, opaque to the actinic rays of light, and the drawing will remain undisturbed. Thus, by a single operation, without photography, the drawing itself becomes by my process the transparent negative printing black lines upon a white ground. It retains its original dimensions, shows all the gradations of shading of the original drawing, transposed as faithfully as by any of the known photographic methods. The parts covered by the opaque varnish hold back the light from a sensitized surface, while the drawing being now a transparency, prints in exact ratio to the amount of pencil used in making it. But by this method, instead of the usual en and ink effect of a line cut, all the delicacy of shading, from white to deep black, is preserved in the reproduction, and in making it gen and pencil can be used on the same rawing.

The opaque solution thus described, and which is mentioned in the claims, is a dye of a deep ruby color, opaque to actinic rays. The particular characteristics of the opaque ent which will penetrate this particular ink or pencil composing the drawing, in ratio to the density of the drawing, and this solution which thus enetrates to the film penetrates into the fifm in this ratio to the density of the drawing. The percentage of water may vary from three to fifteen per cent. of the whole solution, but without water in some appreciable percentage, I have not observed hitherto that I can get penetration of the film by the solution in ratio to the density of the drawing.

I have described the method, the film employed, the ink and pencil, the varnish, and the various steps by way of illustration only, and not as limitations, from which there may be variations without departing from'the spirit of my invention; and I use the word drawing in both this specification and the following claims to designate any picture, lines, shadings or characters made upon a film by handwork or by any process of printing, or by transferring or photographing the same on the film with a substance which may be removed by a suitable solvent, leaving in its place a transparency,

and especially if such transparency may he graduated as to degree of transparency to correspond with the density of the drawing; and I especially contemplate this improved process as applicable to such drawings on the grained gelatin films patented to me as aforesaid, when treated so that they become with the drawing upon them, transparent printing negatives.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is:

1. The process of producing negatives, which consists in producing a drawing upon a transparent film, treating the same with an opaque solution, which renders the surface bearing the drawing opaque, and leaves the drawing unaltered, but penetrates the drawing in proportion to the density thereof, and penetrates the film underneath the drawing in ratio to the density of the drawing; removing the drawing by a solvent, and leaving in its place a transparency graduated as to degree of transparency corresponding to the density of the drawing.

2. The process of producing negatives, which consists in printing an image in greasy ink upon a transparent film, treating the same with an opaque solution, which renders the surface bearing the printed image opaque and leaves the proof unaltered, but penetrates the proof in proporr raeme tion to the density thereof, and enetmtes my hand and afiixed my seal, at Norwich, in the underneath in ratio to t e density the county of New London and State of of the proof, removing the proof by a. $01 Connecticut, this 12th do of A ril, 1912.

vent, leaving in its place a transparency OZIAS ODG [L. s.] 5 graduated as to degee of transparent: cor In presence ofiresponding to the ensit of the proo G; A. TnomsoN,

In witness whereof, have hereunto set JOHN P. HUNTINGTON- 

